Even if you could perfectly predict who is most likely to spread a disease, it still boils down to the trolley problem of whether it's moral to actively kill one person to save the many. And once go down that road, any sort of logical consistency is almost impossible... Never say never! There's plenty of different subjects that touch on biology. The knowledge of my original comment was learned from a public health seminar where no knowledge of chemistry/physics/microbiology was required.I've sometimes wondered if culling (purely in the interest of human survival as a species) would ever be necessary and under what conditions, or even if the human race as it is now would benefit from cull.
Of course, I wish I had the time to learn a great deal more about biology now, but somehow I don't really see it happening.